All about coffee roasting
Want to taste the nuances of your coffee’s origin? Or do you love coffee that’s dark and bold?
Coffee gets its flavor in a few key ways—where it was grown, the growing method, and finally, the roast. Here’s how roasting works and why it matters.
Quick—what color is a fresh coffee bean right after harvest? If you said “green” you got it right!
If you’ve ever seen a coffee plant, then you know that the bean is actually the seed of a fruit, called a coffee cherry. And the seed inside is naturally green because the outer layer of the seed, called the parchment, contains chlorophyll, the chemical necessary for photosynthesis.
Before that seed can transform into your cup of morning magic, it still has a long way to go. Growers have to extract the seeds from the fruit and then send them off to be roasted. Some of the flavors that end up in your brew are already in those little green seeds since the growing location and conditions really matter to the final product. That’s an article for another time.
For now, it’s off to the roasters.
How does coffee roasting work?
The coffee you buy at the store comes in various shades of brown or black based on the roast. But how does it work to roast the seed of a coffee cherry?
Roasting the coffee beans causes a chemical reaction called the Maillard reaction—the same reaction that causes meat or onions to brown at high heat in dry conditions. (Lower heat and wet conditions might result in caramelization instead).
For coffee, roasting at high heat breaks down the chlorophyll and other compounds and produces new compounds that turn the beans brown and gives them their unique flavors. Depending on the darkness of the roast, the green coffee beans will go into a roaster set between 350°F and 450°F.
During roasting, the beans are stirred continuously and any remaining moisture gets sucked out so that the beans are completely dry. The entire process might only take 15 minutes—more or less depending on the roast. Then the beans are cooled and rested, allowing the flavors to develop.
Several variables determine whether your morning coffee has a light brown color and mild flavor, or a deep blackish hue and a bold taste.
The temperature: The higher the temperature, the darker the roast.
The rate at which the temperature increases.
The length of time in the roaster.
What are the different roast types?
You probably already have a preferred flavor and roast. If you’ve been curious about how your favorite bean got its unique roast, here’s a 101.
Light Roast
Beans called “light” or “blonde” fit into this category, and they usually have a lighter color and a milder flavor. That’s due to the short roasting period, usually less than 10 minutes, and lower temperature.
Some people choose light roast because it maintains the original flavor of the seed. So, if you choose coffee based on its origin or growing method, you might prefer a lighter roast to really pick up on the flavors.
Medium and Medium-Dark Roast
Also known as "city" roasts or “full” roasts, these have a darker brown color and a balanced but bolder roasted taste. The roasting process is a bit longer, usually between 10 to 15 minutes, and the temperature is slightly higher than for light roasts.
You might prefer a medium roast if you enjoy the bolder flavor of the roasting but still want to taste the nuances of flavor that come from a coffee plant’s origin.
Dark Roast
If you love a French or Italian roast, then you love the dark side of roasting. These beans are very dark brown and have a strong, robust flavor with a full body. The roasting process for these beans can go up to 20 minutes, and the temperature is the highest of all the roasts.
While the dark roast overshadows the nuanced flavors of the beans’ origin and growing, you might prefer this method if you like the strong flavor—and some say the darker roast is less acidic. According to a few sources, the darker roasts are also higher in certain antioxidants released during the roasting process.
Does roasting affect caffeine?
The short answer here is “not really.”
Because the flavor of a dark roast is so bold, you might think it’s stronger in terms of caffeine too. But the opposite is true, actually. Some caffeine is removed during the roasting process, so darker roasts will have somewhat less caffeine. The difference is pretty tiny though, and you probably can’t tell just by drinking a cup.
Caffeine levels are determined more by the original coffee plant and the brew methods you use.
Visit your local roaster
Want to learn more? In many cities, you can find a local roastery and take a tour. They may even have tasting opportunities so you can experiment with the subtle (and not subtle) differences between bean types and roasts.
Try a Colombian bean and a medium roast or an Ethiopian origin with a blonde roast. There’s a literal world of coffee to explore!